Retainers for sheets, blankets and other bedclothing long have been desirable to prevent pulling loose while sleeping. It is frequently the practice, particularly with children, to tuck the sheets and/or blankets between the mattress and boxsprings along the bottoms and sides thereof. Although the positioning may initially be tight and close to the bed, continual checking is required to ensure that the sheets and blankets have not come loose and pulled away from the bed. One approach for retaining the lower sheet in place is the fitted sheet. Variations in mattress thickness and the tendency for the corners of fitted sheets to come up keep them from being entirely satisfactory. Also the fitted sheet approach is not applicable to the upper sheet.
Known devices for retaining sheets or bedclothing in place are disclosed in U.S. Pat. Nos. 4,541,137; 4,520,518; 4,276,667; 4,461,049; 4,389,744; and 2,791,784. These patents represent a wide variety of clamps and grippers used for grasping a bedsheet or at least a portion thereof and holding the sheet tightly against the mattress. Specifically, U.S. Pat. No. 4,541,137 discloses a clamping device wherein an elongated flat arm is joined perpendicularly to a U-shaped clamp between the legs of which is clamped a portion of the bedsheet or blanket. The flat arm portion is inserted between the mattress and boxsprings so that the clamping portion extends outwardly along the side of the mattress and grasps the edge of the sheet therein. The edges of the bedclothing not grasped by the clamp are tucked between the mattress and boxsprings in the usual manner.
One recurring problem with most of the known devices is that the devices prevent the tucking of the clamped edge portion of the edges underneath the mattress. Therefore, an undesirable wrinkling and pulling of the edges of the sheets and blankets occurs when some portions of the edge can be tucked under the mattress and other portions of the edges cannot be tucked under. Another problem that exists with known devices is that bedclothing can be relatively easily pulled out of the clamps or retainers when tension is applied to the clothing such as occurs during normal sleeping movement. None of the known devices include a means for increasing the gripping action of the retainers as tension is applied to the bedclothing.
The present invention overcomes these problems through a uniquely designed clamping structure which includes a pair of gripping jaws which receive selected portions of the edges of the bedclcthing, which bedclothing is locked into the gripping jaws by a wedge member inserted therein. The design of the wedge member in a preferred embodiment is generally an elongated member having a triangular cross-section of a size somewhat smaller than the opening that exists between the opposing inner surfaces of the gripping jaws. The wedge member is used to feed the sheet(s) into the area between the gripping jaws, along with the bedclothing then locks the bedclothing tightly in the clasp member. The size and the shape of the wedge member are designed so that when tension is applied to the bedclothing, the wedge is caused to rotate in the clasp member and by so rotating the angular edges of the wedge engage and lock tightly against the inner surface of the gripping jaws to exert a locking force against the bedclothing trapped therein (referred to hereinafter as "positive gripping action"). This positive gripping action ensures that as movement on the bedding occurs and tension is applied against the bedding in a way that would normally dislodge the bedclothing, with the present device the bedclothing is held more tightly during such movement and therefore cannot pull out of position. None of the prior art devices exert a positive gripping action on the bedclothing when under tension. Rather, known devices merely press the sheet against the surface of the mattress or lock the sheet between cooperating parts that will pull apart when tension is applied to the bedclothing. For example, in U.S. Pat. No. 4,541,137, the cooperating elements of the latching member will be caused to pull apart when tension is applied to the bedclothing.
The aforedescribed clasp members may be built into the side and end walls of the mattress, provided on a harness that includes longitudinal and transverse straps, or at the ends of separate straps. The straps will exhibit sufficient elasticity to return the sheet to its taut position when the tension is released.